Elastic Memory for Java is an intelligent balloon driver for Java that resides drectly within the Java heap and is able to balloon Java memory in a way that minimally impacts performane. By contrast ESXi's traditional memory management techniques such as the VMware Tools balloon can lead to performance problems when used in VMs running Java. EM4J is new with ESXi 5 and vFabric 5.
Note: For best results download the file and view in slideshow mode. Also it looks awful in OOO so don't use that.